Method and apparatus for cooling foundry castings

ABSTRACT

A method for cooling foundry castings, characterized in that it comprises the steps of: forming a cooling fog by nebulizing a flow of water, exposing a substantial part of the external surface of the casting to said cooling fog, measuring the temperature of the casting, and interrupting the exposure of the casting to the cooling fog when the measured temperature drops below the predetermined threshold.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for coolingfoundry castings.

2. Description of the Related Art

The invention was developed in particular for installations for theproduction of aluminum castings, by gravity or low pressure die-casting.However, the invention is not limited to this sector of use and can beused in all technical sectors in which there is a need to rapidly coolfoundry castings.

In the case of castings of aluminum or similar light alloys, the castingcomes out of the mould at temperatures in the order of 500° C. To becapable of being handled for the operations subsequent to die-cast(flogging, etc.), the temperature of the casting must drop to values inthe order of 120-150° C. or lower.

Cooling the castings in ambient air requires an extremely long time. Thecooling time depends on the weight of the casting and of the sand corescontained therein. In the case of a cylinder head, the cooling time inambient air is in the order of hours.

Installations where castings are cooled in ambient air require largeaccumulations areas in which the pieces are laid for cooling. Thissolution is not very practicable because it uses a large surface of theinstallation as an accumulation storage location for the piecesundergoing cooling and due to the problems that originate from thehandling of the pieces in the cooling area.

Cooling installations are known in which the pieces to be cooled aremade to pass through a forced air tunnel. In a forced air coolingtunnel, the temperature of the pieces drops to the desired value inabout 20 minutes. The problem of forced air cooling tunnels consists inthat the flow of cooling air contains polluting vapors which must beabated before the air is discharged into the atmosphere and thisrequires highly powerful and costly air extraction and treatmentfacilities, also in consideration of the high flow rate of air requiredto cool the castings.

On the other hand, the use of water to cool foundry castings would havethe drawback of causing stresses and warping in the pieces. Moreover,the cooling water would wet the sand contained in the castings, makingdifficult the subsequent step of flogging the castings.

BRIEF SUMMARY OF THE INVENTION

One object of the present invention is to provide a method and anapparatus for cooling foundry castings in a more rapid manner than iscurrently used which allows to overcome this drawbacks.

According to the present invention, said object is achieved by a methodand by an apparatus having the characteristics set out in the claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

The characteristics and advantages of the present invention shall becomereadily apparent in the course of the detailed description whichfollows, given purely by way of non-limiting example, with reference tothe attached drawings in which:

FIG. 1 is a lateral schematic view of an apparatus for cooling foundrycastings according to the present invention and

FIG. 2 is a plan schematic view of the apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, the reference 10 designates an apparatusfor cooling foundry castings. The apparatus 10 can be installed in aninstallation for the production of aluminum castings, by gravity or lowpressure die-casting. The cooling apparatus 10 receives the foundrycastings at the output of the mould and cools them down to a temperaturewhereat the castings can be subjected to the subsequent operations, suchas flogging, etc.

The apparatus comprises a cooling chamber 12 within which is provided asupport base 14 able to support a foundry casting 16. The figures show,by way of example, a casting constituted by a head for an internalcombustion engine of a vehicle. Naturally, it is understood that themethod and the apparatus according to the present invention can be usedfor cooling castings of any type and material. The foundry casting 16which is subjected to the cooling operation is further provided with theriser and with the pouring channels 18 and contains the cores of sandagglomerated with resins which are used to form channels, seats andcavities of various types in the structure of the castings.

In the example illustrated in the figures, the cooling chamber 12 hasthe shape of a parallelepiped with rectangular base and is provided withat least one opening for the introduction and the extraction of thecasting 16. In the illustrated example, the cooling chamber 12 lacks oneof the two vertical walls with smaller sides in order to form an opening20 contained in a vertical plane which allows the introduction andextraction of the casting along a horizontal direction indicated by thedouble arrow 22. The casting 16 is preferably introduced and extractedby means of an automatic manipulator device (not shown) constituted forexample by an anthropomorphic robot.

Alternatively, the cooling chamber 12 could be constructed in the formof a tunnel with a motorized conveyor which extends through the coolingchamber and which transports the castings through the chamber. Saidconveyor could be capable of being operated in steps to maintain thecasting in stationary position during the cooling time and to carry thecooled casting outside the cooling chamber at the completion of thecooling step.

The cooling chamber 12 contains means able to create a cooling fogformed by a suspension of very fine water droplets. Preferably, themeans for generating the cooling fog comprise a plurality of nebulizerguns 24 fed by a jet of water under pressure produced by a pump 26,preferably electrically or pneumatically operated. When the nebulizerguns 24 are fed by a flow of water under pressure, produce a fog formedby very fine water droplets in suspension in the air which fills theinternal volume of the cooling chamber 12 surround the foundry casting16 and its riser 18. The cooling fog is not projected onto the externalsurface of the casting but forms a substantially static cloud whichsurrounds the casting to be cooled. In contact with the casting at hightemperature, the cooling fog vaporizes, removing the heat ofvaporization of the water from the piece. The fog comes in contact withthe surface of the piece in uniform fashion, without producing suddenlocal cooling which could generate stresses or warping in the structureof the piece.

The cooling chamber 12 is provided with a temperature measuring device28 able to measure the temperature of the casting 16 housed within thecooling chamber 12. The temperature measuring device 28 comprises asensitive element 30 (FIG. 1) which is placed in contact with a point ofthe casting 16 and is maintained in contact with the piece 16 throughoutthe cooling step.

The sensitive element 30 of the temperature measuring device 28 can be athermocouple. To enhance the accuracy of the temperature measurement,the sensitive element 30 is placed in contact with a wall of a cavity ofthe casting 16 open inferiorly. In this way, the sensitive element 30 issubstantially sheltered from the action of the cooling fog. Thesensitive element 30 must remain in contact with the casting 16. Toobtain this, the sensitive element can be positioned at the end of alever 32 articulated to the base 14 and provided with a counterweight 34which tends to maintain the sensitive element 30 in contact with thewall of the lower cavity of the casting 16.

The temperature measuring device 28 provides an electric signal,indicative of the temperature of the casting 16. This signal is receivedby a control unit 36 which compares the measured temperature with apredetermined threshold temperature. The control unit 36 is provided tointerrupt the feeding of the pump 26 when the measured temperature dropsbelow the reference threshold. For example, the feeding of the pump 26,and hence the generation of fog in the cooling chamber 12, can beinterrupted when the measured temperature drops below about 130-140° C.

When a hot casting 16 is introduced into the cooling chamber 12, thetemperature measuring device 28 measures its temperature by means of thesensitive element 30. When the measured temperature exceeds a referencechamber, the pump 26, which generates the cooling fog, is started. Theproduction of the fog continues until the measured temperature dropsbelow the reference threshold. Interrupting the production of fogaccording to the measured temperature of the casting 16 allows toprevent the fog from being deposited on the piece, wetting the sand.Assurance is thereby provided that the castings exiting the coolingchamber 12 are perfectly dry. Therefore, even if the cooling operationis performed in the presence of water, the subsequent step of floggingthe pieces is not compromised in any way.

The cooling system according to the present invention is extremelyefficient. Within a few minutes (4-6 minutes) the temperature of acasting with a weight, including the cores, in the order of 40-50 kg isreduced from about 500° C. to about 130-140° C.

As an alternative to the illustrated solution which entails theactivation and deactivation of the pump which generates the cooling fog,a solution can be obtained in which the fog is produced in continuousfashion and the casting is moved outside the operating range of thecooling fog when the temperature measured of the casting drops below thepredetermined threshold.

1. A method for cooling foundry castings, comprising the steps of:forming a cooling fog by nebulizing a flow of water, exposing asubstantial part of the external surface of the casting to said coolingfog, measuring the temperature of the casting, and interrupting theexposure of the casting to the cooling fog when the measured temperaturedrops below the predetermined threshold.
 2. Method as claimed in claim1, wherein the cooling fog is formed within a cooling chambersurrounding the casting.
 3. Method as claimed in claim 1, wherein theformation of the cooling fog is interrupted when the measuredtemperature of the casting drops below said predetermined threshold. 4.Method as claimed in claim 1, wherein the casting is moved outside therange of operation of the cooling fog when the measured temperaturedrops below said predetermined threshold.
 5. Method as claimed in claim1, wherein the temperature of the casting is measured by bringing asensitive element in contact with a surface of the casting at leastpartially sheltered from the action of said cooling fog.
 6. An apparatusfor cooling foundry castings, comprising: a device for producing acooling fog by nebulizing a flow of water, an element for measuring thetemperature of a foundry casting whilst a substantial part of theexternal surface thereof is exposed to the action of said cooling fog,and a controller for interrupting the exposure of the casting to theaction of said cooling fog when the measured temperature drops below thepredetermined threshold.
 7. An apparatus as claimed in claim 6,comprising a cooling chamber containing at least one nebulizing gun. 8.An apparatus as claimed in claim 6, wherein said element for measuringthe temperature of the casting comprises a sensitive element which inuse is placed in contact with a surface of the casting at leastpartially sheltered from the action of the cooling fog.
 9. An apparatusas claimed in claim 6, wherein said controller is able to interrupt thefeeding of the water flow to said means for forming the cooling fog. 10.An apparatus as claimed in claim 6, wherein said controller is able tomove the casting outside the range of action of said cooling fog.